6.2 Nervous coordination

• nerve impulses are how information is sent through the nervous system
• a nerve is a bundle of neurones
• neurones have a long fibre known as an axon
• the axon of some neurones is insulated by a sheath made of myelin
• myelin is made by specialised cells known as schwann cells
• schwann cells being present means that electrical impulses jump from one node to the next rather that travelling down the whole axon
• what are the 3 main types of neurones?

  sensory, relay and motor
• sensory neurones carry impulses from receptors to the CNS
• relay neurones connect sensory and motor neurones
• motor neurones carry impulses from the CNS to effectors
• what is the usual reasting potential of neurones?

  -70mV
• stages in order of what happens to the potential difference of a neurone after a stimulus?

  stimulus, depolarisation, repolarisation, hyperpolarisation, resting potential
• what is the usual threshold for PD across a membrane?

  -55mV
• what is the usual max PD across a membrane?

  30mV
• how does an action potential move along a neurone?

  wave of depolarisation
• what is that nature of action potentials?

  all-or-nothing
• what are the 3 factors that affect the speed of conduction of action potential?

  myelination, axon diameter, temperature
• what is a synapse?

  a junction between two nerve cells where electrical or chemical signals are transmitted.
• neurotransmiters can be excitatory, inhibitory or both
• summation is when the effect of the neurotransmitter is multiplied by the number of receptors
• what are the two types of summation?

  spatial, temporal
• in spatial summation, there are more than one postsynaptic membrane activated at once
• in temporal summation, there are repeated stimuli over time
• what neurotransmitter do neuromuscular junctions use?

  Acetylcholine